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Thursday, April 11, 2019

Aircraft Impact Damage to the WTC Perimeter Columns

No Evidence of Explosive Detonations Upon Impact

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A review of the damage to the perimeter columns at the World Trade Center Twin Towers on 9/11 only shows the effects of a large momentum impact.  The damage does not suggest the presence of explosive detonations upon impact. 

Aircraft impact damage to the perimeter columns of the World Trade Center Twin Towers is one topic where the 9/11Truth Movement has been subjected to a continuous barrage of misinformation. In a recent internet debate between three members from the “anything but a large plane impact into the Twin Towers,” perspective, the proponents argued – without discussing the observed damage – what caused the openings in the sides of the Twin towers. These three debaters were introduced by the moderator as knowledgeable and addressing the issue from "diverse perspectives."

Unfortunately, there was no person included in the debate with enough knowledge to explain that the damage was caused by a large momentum impact. The three debaters all agreed that the damage must have been caused by explosive detonations either pre-planted or delivered by missiles – but in their opinions – anything but a large plane impact caused the damage. A listener to this debate might have come to the conclusion that these three debaters represented a consensus of the 9/11 Truth community.

Standards of Evidence

The 9/11 truth community has coalesced around the rigorous work of Architects for 9/11 Truth and the Lawyers’ Committee for 9/11 Inquiry because of their analysis and their standards of evidence. These two organizations are viewed as adhering to the scientific method which – as Scientists for 9/11 Truth observe – was developed painstakingly, over the past centuries, sometimes at great cost to personal reputation, circumstance, and freedom, and even to life itself.

The scientific method requires the collection, study, and analysis of factual information and data regarding the events that took place on September 11, 2001 (e.g., 9/11). Responsible organizations demanding accountability for the events of 9/11 must demonstrate the highest standards of evidence to garner public support for a new, independent and scientific investigation of the events of 9/11. To succumb to a lower standard would be a dis-service to the victims of 9/11and the resulting 9/11 related wars.

While not all information is known about the events of 9/11, a careful evaluation of the available evidence can lead to a better understanding of what happened on that day – and lead to a more effective outreach in the quest for a new investigation.

Plane Impact or an Explosive Hoax

A review of the evidence shows that the damage to the sides of the Twin Towers is consistent with a large momentum impact. Furthermore, the observed damage cannot be explained by explosive detonations – whether large or small. Explosives do not work “by magic” – explosives cannot sculpt damage that resembles a large momentum impact while failing to leave other damage that would be inconsistent with a large momentum impact.

Explosive detonations have four basic characteristics:

  • Explosive detonations are caused by a chemical compound or mixture ignited by heat, shock, impact, friction, or a combination of these conditions;
  • Upon ignition, it decomposes rapidly in a detonation;
  • There is a rapid release of heat and large quantities of high-pressure gases that expand rapidly with sufficient force to overcome confining forces, and
  • The energy released by the detonation of explosives produces four basic effects that operate in all directions from the epicenter;
    • Fragmentation
    • Displacement
    • Ground vibration
    • Air blast

When doing outreach among the public related to 9/11, occasionally someone who is aware of the events of 9/11 may state their disbelief that there were any planes involved in 9/11. During the 2018 anniversary there was a resurgence of comments about the shape of the outline of the plane on the side of the WTC Twin Towers – with the assertion that the plane could not have gone through the tower as observed. Those commenters referred to the plane passing through the Twin Towers in a manner similar to a "Wile E. Coyote" impact (from the Looney Tunes and Merrie Melodies Cartoon series). These characterizations of the impact are incorrect and a review of the damage shows that the damage can only be explained by a large plane impact.

The review shows that much of the observed damage to the exterior perimeter columns was in the area near where the center of the plane's mass impacted the building (center of mass is between, and including, the engines). At the locations where the "light" ends of the wings (e.g., lower mass) impacted the Towers, the aluminum cladding on the columns suffered significant damage, but the wings did not penetrate the exterior perimeter columns in these areas.

Previous articles on have described the tower sway resulting from momentum transfer and the deceleration of the tail of plane impacting the South Tower. These effects are inconsistent with explosive detonations.

Perimeter Columns Construction Details

WTC Perimeter Columns annotated 39b49 copyFigure 1: Perimeter column "Trident" panel. Click to enlarge.The exterior perimeter columns were closely spaced to form a stiff bolted-together tube that was designed to resist the wind loads and carry a portion of the gravity load. The individual columns were roughly 14 in. square, and were fabricated by welding individual plates into box columns. Perimeter column sections consisted of three adjacent columns, each three stories high, that were joined by horizontal spandrel plates where floor trusses were connected. Figure 1 shows a three-story tall, three-column wide, trident exterior wall panel in place.

Nearly every panel assembly was unique, and each was intended for a specific location on a given face of one building. In the lower floors, the individual plates that made up the perimeter columns were up to 1 in. thick, but those in the impact floors were typically 0.25 in. thick. Additionally, because the wind loads differed between the different compass directions, the distribution of column strengths and thicknesses on each face of each building was unique; the two towers were not identical copies. Once in place, the panels were bolted together to neighboring panels at the spandrel connections.

The exterior perimeter columns were connected to each other, above and below, by four A325 7/8" bolts that passed through an end butt plate (e.g., at a "column splice"). Perimeter columns were only welded together at the mechanical floors. As will be shown, it is at the location of these bolts that the perimeter column splices failed due to shear forces, breakage or pull-out.

With these modes of bolt failures, the perimeter columns are seen mostly destroyed at the ends of the trident sections. Significant bending of the steel perimeter columns can occur once a splice has failed.

The photographic record for the damage to the North Tower is more complete than for the South Tower.  Because of the fewer locations from which the high-resolution photographs of the South Tower damage could have been taken, few good photographs exist.  Consequently, only the North Tower will be discussed in this article.

Map of Trident Panels in North Tower Impact Area

To facilitate the discussion of damage to the North Tower, the damaged area has been marked off into a grid of 90 numbered squares. Each of the the horizontal lines represent a level where the trident panels are bolted together.  In Figure 2, the panels are color coded to show how they are staggered across the floor levels.  As shown in Figure 2 (complementing the example of the staggering shown in Figure 1), the panels are staggered so that adjacent tridents reinforce each other vertically across three floor levels to provide strength in high winds.   Figure 3 (see below) shows the same area of the North Tower with the grid superimposed on a photograph of the damage.

WTC Perimeter Columns NIST annotated 11aa4 copyFigure 2: North Tower damage map showing the trident panels. Click to enlarge.

As shown on Figures 2 and 3 (see below), the upper right side of the grid is the extent of the damage to the facade caused by the right wing (see grid square 15).  The damage caused by the left wing can be seen at the lower left (see grid square 76). 

The area where the body of the plane impacted is centered around grid squares 53 and 54.  Figure 2 does not indicate any panels in this area because there are none shown in Figure 3.  As shown in this Figure 3, most of the openings begin at a splice where one trident section was bolted to the next trident above/below it.  This is indicative of bolts failing at the butt ends where the connections were joined. 

The accuracy of the damage documented in the schematic shown in Figure 2 can be verified against the photograph in Figure 3.

Physical Map of North Tower Impact Area

Figure 3 shows the damage with the location grid superimposed.  Using this location grid, the corresponding trident panels can be matched to the color coded tridents in Figure 2.  The photograph shows more detail to better understand the failure mechanism of the perimeter columns.

NorthTower Damage Map 83180 copyFigure 3: North Tower damage map.  Click to enlarge.

A review of the photographs shows that the extremities only sustained damage to the outer skin of the aluminum cladding.

Left Wing-End Damage Only to Aluminum Cladding

Left wing impact area shows 30 feet of damaged aluminum cladding with intact perimeter columns.

NorthTower Damage V2 c397b copyFigure 4: Left wing impact area shows 30 feet of damaged aluminum cladding with intact perimeter columns. Click to enlarge.For an even higher resolution image, click here.

The left wing impact area shows about 30 feet of damaged aluminum cladding with the underlying perimeter columns intact.

Right Wing-End Damage Only to Aluminum Cladding

The right wing impact area shows about 20 feet of damaged aluminum cladding with the underlying perimeter columns intact. The NIST schematic indicates damage to the columns in grid cell 14, but they are visible and appear to be continuous and not separated or seriously compromised. 

WTC RightWingImpact fd964 copyFigure 5: Right wing impact area shows 20 feet of damaged cladding with intact perimeter columns. Click to enlarge.

The NIST schematic indicates damage to the trident panel in grid cell 14, but the columns are visible and appear to be continuous.  They do not appear separated or seriously compromised. 

The left-most column of the the trident panel splice between grid cells 14 and 29 appears to have separated.  This separation is at the location of the bolted connection where failure could be expected.

Perimeter Column Splice Failure

At many of the locations where the perimeter column trident panels were spliced together, they are seen cleanly separating.   Figure 6 shows a number of the locations (schematic vs. photo) where the columns separated due to bolt failures.

WTC SpliceFailures b1e15 copyFigure 6: Example locations of column splice failures. Click to enlarge.

Photographic and structural debris evidence clearly demonstrated that the external column connection failures played a significant role in the mode of column failure and the extent of the external damage.

Perimeter Column Splice-End Bolt Failure

Many steel perimeter column sections were photographed in the post-demolition debris.  In those photos, evidence that the connecting bolts failed is clear.  In some cases the butt plates are visibly deformed, but in most others the bolts are either completely missing or obviously mangled.  The butt end shown in Figure 7 shows one failed bolt and three missing.   WTC Bolted Connection Failure 7257f copyFigure 7: Bolted connection failures at butt-end splices. Click to enlarge.


Spandrel Connection Bolt Failures

Another point of failure was at the spandrel connections.  At these locations, the horizontal plates (refer back to Figure 1 which shows where the floor trusses were connected) also connected the adjacent trident panels together.  These spandrels were bolted together using an intermediate connection plate.  In Figure 8, the right side of the image shows the spandrel has been bent and the steel was fractured when the bolt was pulled through. On the left side of the image, the intermediate connection plate is shown still attached to one side of the spandrel connection.  

WTC Spandrel Bolt Failure e7012 copyFigure 8: Spandrel bolt failures showings missing bolts (left) and "torn" bolt holes (right). Click to enlarge.

Weld Failures

Another failure mechanism that is observed in the photos relates to the separation of the component pieces of the perimeter columns themselves along the welds.  The perimeter columns were made of steel plates that were welded together into 14 inch square columns.

WTC Weld Failure annotated v2 e37ec copyFigure 9: Impact area, perimeter column weld failure (upper) and annotated (lower). Click to enlarge.

Photographs of the damage immediately after impact, and inspection of the recovered trident panels from the impact zone, show that failure along the welds (heat affected zones) was a characteristic feature of the impact damage. An example exterior column from the impact area which had significant fractures along the weld zone for the outer web is shown in Figure 9.  In this example, the weld fracture progressed along the weld until it reached the internal stiffener at the location of the spandrel.

Perimeter Column Weld Failures Near Grid Square 78

Figure 10 shows the area near grid location 78, where three columns clearly illustrate weld failures similar to those shown in Figure 9.

WTC_GridSquare78_8baed.pngFigure 10: Perimeter columns exhibit weld failures.

The left most column in grid square 78, labeled as column 78a, shows that the weld along the right side of the column 78a has separated and the right side plate is pulled to the right (see the yellow arrow).  This effect is more pronounced with the middle column, labeled as column 78b, where the right plate has separated and is also pulled to the right. These two particular columns with their weld failures, and the resulting elongated shape of their right side plates, is strongly suggestive of damage caused by the wing structures (including the leading wing spar) impacting – and interacting with – these columns. The impact would have fractured the weld and the wing structure would have grabbed/pulled the plates toward the interior of the Tower due to the momentum of the heavier mass of the wing root and (its still attached?) engine.

The weld failures in the right most column of grid square 78, identified as column 78c, are the most severe.  This column appears to be the only column that has obviously been severed at a location remote from the bolted connections of a butt-end splice.  The upper half of the column is seen pulled down (see grid square  63) and separated at the bolted splice to the column above it (grid square 48).  The rightmost yellow arrow shows that the right plate of column 78c has been bent and pulled to the same rightward direction as the right plates of columns 78a and 78b. 

Close Examination of Perimeter Column Damage - Specimen #1

At the 9/11 Memorial Museum in New York, it is possible to view remnants of the perimeter columns from the impact area. 

WTC damaged steel beam Wikipedia a4ca8 copyFigure 11: Wall mounted perimeter column on display. Click to enlarge.  Source Gabichan2020 (via Wikipedia)

Specimen #1 is wall mounted and shows the weld failures, bends and one type of spandrel connection failure.

Close Examination of Perimeter Column Damage - Specimen #2

A second perimeter column that is available for inspection is a freestanding piece that spanned floors 93-96 of the North Tower.

WTC North Tower floors 93 96 1c354 copyFigure 12: This piece shows very significant weld failures and other mechanisms of failure. Click to enlarge. Source: Beyond My KenThis piece shows very significant weld failures and other deformations.


The damage to the face of the North Tower can only be explained by the impact of a large plane.  The dimensions are consistent with those of a Boeing 767. The damage to the columns can only be explained by a large momentum based impact.  It is not possible for explosive detonations to have created the widespread pattern of inwardly focused (e.g., pushed) damage.  Explosives would have created epicenters where damage would have emanated in all directions outward from the point of detonation – and no damage fitting this description is observed in the impact area.

As with the Pentagon, a detailed analysis of damage to the World Trade Center Twin Towers provides solid evidence for what actually happened. 

 The Woman in the Tower

WTC NorthTower EdnaCintron square d9075 copyFigure 13: The woman in the tower.

A woman is visible near the top right of grid square 61– on about the 97th floor.  In a number of photographs, she is seen holding on to a severed pillar, waving. She has been identified as Edna Cintron, an employee with the insurance brokers Marsh & McLennan. Cintron's husband reportedly confirmed her identity.


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